Modern oil field operations demand a great quantity of information relating to the parameters and conditions encountered downhole. Such information typically includes characteristics of the earth formations traversed by a borehole, and data relating to the size and configuration of the borehole itself The collection of information relating to conditions downhole, which commonly is referred to as “logging,” can be performed by several methods including wireline logging and “logging while drilling” (LWD). In wireline logging, a probe or “sonde” is lowered into the borehole after some or the entire well has been drilled, and various parameters of the earth's formations are measured and correlated with the position of the sonde in the borehole as the sonde is pulled uphole. Meanwhile, in LWD, the drilling assembly includes sensing instruments that measure various parameters as a formation is being penetrated.
One type of logging, referred to as induction logging, measures the resistivity properties of formations by generating and measuring electrical currents and/or voltage potentials from which one determines formation resistivity. Another type of logging, referred to as acoustic logging, measures the acoustic properties of formations by transmitting an acoustic wave through the fluid in a well and surrounding elastic materials and then measuring the travel time, amplitude, or other attributes of reflected waves.
Acoustic logging and induction logging are typically performed by separate tool sections along a logging string. This arrangement increases the length of the logging string and does not allow simultaneous acoustic logging and induction logging of the same formation.
The drawings show illustrative embodiments that will be described in detail. However, the description and accompanying drawings are not intended to limit the invention to the illustrative embodiments, but to the contrary, the intention is to disclose and protect all modifications, equivalents, and alternatives tailing within the scope of the appended claims.